microorganisms that are similar to bacteria in size and simplicity of structure but radically different in molecular organization. They are now believed to constitute an ancient intermediate group between the bacteria and eukaryotes.
FULL ANSWERArchaebacteria, or archaeans, are single-celled organisms. Although they were first classified with bacteria, they have since earned their own category. While they have a simple structure much like bacteria, there are many differences. They have a unique type of rRNA that sets them apart from their fellow prokaryotes. Furthermore, they do not cause sickness in people.Archaebacteria are considered extremophiles because they live in a variety of harsh environments and can tolerate extreme conditions such as, acidity and salinity. They are divided into three main groups: crenarchaeota, euryarchaeota and korarchaeota.Crenarchaeota consist of hyperthermophiles and thermoacidophiles that thrive in very hot, cold or acidic environments. Euryarchaeota consist of halophiels and methanogens that thrive in salty and oxygen-free environments. For example, euyarchaeota often live inside in the guts of animals. Compared to other the other groups of archaebacteria, less is known about korarchaeota. Scientists do konw that they are thermophilic and live in hot springs.
